baseline problem of HPLC

[julietinmay]

I am running HPLC samples use the same method and same sequence except I prepare a new mobile phase A which is 0.1% TFA in water. There appeared 3 huge peak in my blanks .
Another analyst reprepare the mobile phase, we changed mobliphase B and C ( ACN and IPA) and cleaned the system and aloso change another used column. but there is still something on my baseline. I realzied it might cause by water, so I used bottled HPLC water. the base line are not that bad, the noise peak decreased from 0.02 to 0.005 and they are not 3 peaks anymore but they changed to one with a small negtive peak there. Right now I am using good water, ACN and IPA try to clean my system, what else I can do?
how can I post picture?
By the way, the method was running all days long for few months and nevery has such problem. it is gradient from 90% TFA to 70% ACN with 5%IPA in 3.5 minutes and stay there for 1.5 minutes and back to 90% TFA . the column is a 10cm column and the detect at 278nm.
those peaks shows up at 2.5-3 minutes.

[tom jupille]

This is one of the more common questions that gets asked on the Forum. Watch this video for a discussion of what's going on and a diagnostic test to confirm the cause of the problem (you will have to register separately). http://www.lcresources.com/more_resourc ... hp?f=3&t=5

[julietinmay]

thank you very much. they are very helpful. I think the problem comes from the water. But how can I get fird of it. It used to be very good baseline. We used to use millQ system and we changed erverything we can change. And we changed the water to HPLC grade water, the baseline is better but not enough. And based on the website you posted, I double check, the problem comes from the solvent A. I plan to by deion water instead, hope it helps.

[tom jupille]

You might also try the "Empore" filtration trick:
www.chromforum.org/viewtopic.php?f=1&t=130